1. Field of the Invention
The present invention relates to a component mounting method and device which are used in a component mounting apparatus for mounting an electronic component on an electrode in a process of mounting operation in which a paste of cream solder is applied on an electrode on a circuit board, on which an electronic component which is positioned above the electrode is mounted, after which the cream solder is heated and melted to join the component onto the electrode.
2. Description of the Related Art
FIG. 4 is a plan view typically showing a primary structure of a component mounting device, in which a plurality of parts cassettes 42 in a component feeding unit 43, respectively accommodating different types of electronic components, are moved to a position where the component is picked up by a suction nozzle unit 41 in the order of mounting onto the circuit substrate 44.
The suction nozzle unit 41 has a rotary structure, which is constructed such that a plurality of suction nozzles 40 mounted thereon are successively moved on a circular track for picking up an electronic component from the parts cassette 42 in the component feeding unit 43 and mounting it onto the circuit substrate 44 which has been loaded to a mounting position. The suction nozzle unit 41 rotates to successively transfer each of the suction nozzles 40 from the positions denoted at encircled numerals 1 to 10 in a clockwise direction as shown in the figure. The electronic component is picked up from the parts cassette 42 at a component pick-up position (component pick-up point) denoted at encircled numeral 5, the picked-up posture of the component is recognized with image recognition process using a camera at a posture recognizing position (component recognizing point) denoted at encircled numeral 7, and the posture of the component is corrected around the axis of the suction nozzle 40 by its rotation based on the recognition results of the picked-up posture of the component at a posture correcting position (component position adjusting point) denoted at encircled numeral 9.
Meanwhile, the circuit substrate 44 is supported on an X-Y table (not shown) for free movements in X- and Y- directions, so as to bring a predetermined position of the circuit substrate 44 on which an electronic component is to be mounted is brought under a component mounting position (component mounting point) denoted at encircled numeral 10 of the suction nozzle unit 41. The circuit substrate 44 is also moved in directions for correcting displacement of the component in X- and Y- directions based on the picked-up posture recognition results. It is thus possible to mount an electronic component 45 picked up by the suction nozzle 40 which is displaced as shown in FIG. 5 precisely on the predetermined position on the circuit substrate 44.
However, in high density chip mounting of recent years, the space between two adjacent components have become smaller and smaller. As a result, especially in the case where the outer dimensions of the component are smaller than those of the suction nozzle, and under a condition that the center of the suction nozzle and that of the component are not in register with each other, it is often the case that the suction nozzle and an electronic component which has previously mounted on the circuit board interfere with each other, thus causing mounting errors. As shown in FIG. 6, for example, when mounting the electronic component 45 picked up by the suction nozzle 40 next to the electronic component 46 which has already been mounted on the circuit substrate 44, if the electronic component 45 held with the suction nozzle 40 is displaced from a prescribed position of the nozzle, the suction nozzle 40 which is lowered so as to mount the electronic component 45 to a predetermined position will hit the electronic component 46 previously mounted, which may cause the component 46 to be tilted or sprung out.
Also, the electronic component mounting device has an automatic recovery function in the case of failing to mount a component due to errors in picking up action, which is implemented such that the component which the nozzle failed to mount is mounted after all the other components have been mounted. In such a case, since the mounting order is different from the normal one, the component has to be mounted between the other components which have already been mounted, wherefore if the position of the component held by the suction nozzle is displaced, it is more often the case that the suction nozzle and the previously mounted component interfere with each other, causing frequent errors in mounting operation of the components onto the circuit substrate 44. In particular, it may cause a serious problem if the height of the component which has already been mounted is larger than that of the component which is going to be mounted later.
In view of the foregoing, an object of the present invention is to provide a component mounting device and method, by which, when mounting components onto a circuit substrate, the quality of mounted conditions of the components is kept favorable without causing any interference between the previously mounted component and the nozzle, even when the center of the nozzle and that of the component are not correspondent to each other.
In order to achieve the above object, the component mounting device of the present invention comprises a means for measuring an amount of displacement between a center position of a component suction nozzle and a center position of the component held by the component suction nozzle with respect to each of the components fed from all parts cassettes set in a component feeding unit during the component mounting device is in operation, informing that a particular parts cassette from which the component has been fed is in abnormal condition when the amount of displacement is larger than a predetermined value, and for stopping the action of mounting the component.
With this arrangement, under a certain abnormal circumstance while the device is in operation, it is informed to an operator that abnormality has been occurred as well as the mounting action is stopped, thereby preventing interference between the component suction nozzle and the component, and enabling the operator to investigate and confirm the causes of the abnormality.
Further, the device comprises a means which measures an amount of displacement between a center position of a component suction nozzle and a center position of a component held by the component suction nozzle, and detects and informs that a particular component suction nozzle or parts cassette from which the component has been fed is in abnormal condition based on resultant data of measurement, wherein the component is respectively picked up by the component suction nozzle from all of the parts cassettes set in a component feeding unit and measurement of the displacement amount of the component is effected in a preparatory step before commencement of actual production.
By this means, defective nozzles or parts cassettes are identified prior to actual production, by which mounting errors when mounting the component onto the circuit substrate can be avoided.
Also, in order to achieve the above object, the component mounting method of the present invention comprises the steps of: measuring an amount of displacement of the component with respect to the component suction nozzle; and adjusting the component pick-up position of the parts cassette which requires position adjustment based on resultant data of measurement.
More specifically, the method comprises the steps of: obtaining data on an amount of displacement of the component from a prescribed holding position of the component suction nozzle corresponding to each of the parts cassettes based on posture recognition results detected at the posture recognizing position; and adjusting a feeding position of the electronic component to the component pick-up position based on this displacement amount data.
According to the above described component mounting method, from the data on the posture of the component held by the component suction nozzle with respect to all the electronic components detected at the posture recognizing position, the data on displacement amount of the component per each parts cassettes can be obtained, wherefore the tendency of displacement in the component feeding position with respect to the pick-up position of the suction nozzle can be recognized. Specifically, if it is found that all of the electronic components are displaced in the same direction, it is determined that the position of the component feeding unit or the parts cassettes in its entirety is inappropriate in relation to the component pick-up position, whereas if it is found that only a specific type of electronic components are always picked up in a displaced position, it is determined that the feeding position of the parts cassette which feeds this type of electronic component is inappropriate. Accordingly, by adjusting the component feeding position to the component pick-up position in a direction for correcting displacement based on the displacement tendency obtained from displacement data, it is possible to pick up the component precisely in a predetermined position of the component suction nozzle, whereby it is possible to mount electronic components accurately on the circuit substrate with high mounting density.
If it is detected from the displacement amount data that all of the electronic components are picked up in a displaced position in the same direction, such displacement can be corrected by adjusting the position of the component feeding unit or the loading position of the parts cassettes on the component feeding unit in a direction for correcting the displacement. Also, if it is detected from the displacement amount data that one specific type of electronic component is picked up in a displaced position, such displacement can be corrected by adjusting the component feeding position to the component pick-up position from the parts cassette which feeds this type of component.
Also, in order to achieve the above object, the device for mounting an electronic component in which a plurality of parts cassettes respectively accommodating different types of electronic components are moved by a component feeding unit to a component pick-up position in a mounting order for feeding electronic components, and a plurality of component suction nozzles are successively moved along a circular track from the component pick-up position, where the component suction nozzle picks up the electronic component, to a posture recognizing position, where the posture of the electronic component held with the component suction nozzle is detected, based on which the position and angle of the electronic component in relation to a predetermined position on a circuit substrate are corrected, and further to a component mounting position, where the picked-up electronic component is mounted on the predetermined position on the circuit substrate, according to the present invention, comprises: a displacement amount data processing means for obtaining data on an amount of displacement of the electronic component from a prescribed holding position of the suction nozzle corresponding to each of the parts cassettes based on posture recognition results detected at the posture recognizing position, and a drive means for moving the component feeding unit or the parts cassette so as to adjust the component feeding position to the component pick-up position in a direction for correcting the amount of displacement of the electronic component which is obtained from the displacement amount data.
With the above described structure, from the data on the posture of the component held by the nozzle with respect to all the electronic components detected at the posture recognizing position, the data on displacement amount of the component per each parts cassettes can be obtained by means of the displacement data processing means, wherefore the tendency of displacement in the component feeding position with respect to the pick-up position of the component suction nozzle can be recognized. Specifically, if it is found that all of the electronic components are displaced in the same direction, it is determined that the position of the component feeding unit or the parts cassettes in its entirety is inappropriate in relation to the component pick-up position, whereupon the component feeding unit or the entire group of parts cassettes is moved in a direction for correcting the displacement based on the obtained amount of displacement. Also, if it is found that only a specific type of electronic components are always picked up in a displaced position, it is determined that the feeding position of the parts cassette which feeds this type of electronic component is inappropriate, whereupon the feeding position of the parts cassette which feeds the component is adjusted.